The expression absorbent products is used here to denote diapers, sanitary towels, panty liners and incontinence articles.
Previously disclosed are a large number of processes for the manufacture of absorbent products, although a feature common to all these processes is the desire to achieve the highest possible rate of production. One way of achieving a high rate is to arrange the production facility in such a way that a continuous process is obtained, in which a plurality of material webs is brought simultaneously and continuously to different process stations for slitting, cutting, stretching of the material, shrinking, joining, etc., in order finally to obtain the finished product. The manufacture of an absorbent product is thus subject to special conditions, which means that the process is difficult to compare with another process, for example in the case of the manufacture of automobile components or in the ready-made garments industry.
The execution of slits in a layer of material by causing the layer of material to pass between a slitting tool and an abutment roller, which rotate in opposite directions relative to one another, is already familiar in the manufacture of absorbent products. The abutment roller has a circular cross section, and the slitting tool has a cutting edge which includes intermittently raised parts intended for cutting or perforating the layer of material.
The raised parts are pressed against the abutment roller in order for the cutting edge to produce its effect through the layer of material and, in this way, to bring about the desired slits.
One problem associated with the prior art is that the intermittent raised parts cause vibrations when the rollers rotate against one another, because the slitting tool does not have a circular cross section, and consequently give rise to an unequal pressure during rotation. The vibrations have the disadvantage that the manufacturing facility can only operate at a limited speed, because other parts of the machine and suspensions would otherwise be exposed to the risk of being shaken apart or affected by fatigue problems. A further disadvantage is that the wear on the slitting tool is considerable because that part of the cutting edge which first enters into engagement, after a period when the slitting tool is not in engagement with the abutment roller, is required to take up all the force unaided, which results in a shorter service life.
A wish and a need accordingly exist for an improved manufacturing process for slitting layers of material in conjunction with the manufacture of absorbent products.